071 FXUS66 KSGX 121118 AFDSGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN DIEGO CA 415 AM PDT SUN OCT 12 2008 .SYNOPSIS... PERIODS OF MODERATE TO LOCALLY STRONG SANTA ANA WINDS AT TIMES THROUGH TUESDAY WITH THE MOST WIDESPREAD AND STRONGEST WINDS LATE TONIGHT THROUGH MONDAY AFTERNOON. WARM AND DRY BUT WITH WEAKER WINDS FOR MIDWEEK. WEAK ONSHORE FLOW WILL BRING COOLING AND A RETURN OF THE MARINE LAYER BY NEXT WEEKEND. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (SUNDAY THROUGH TUESDAY)... AN UPPER TROUGH OF LOW PRESSURE EXTENDS FROM EASTERN MONTANA INTO SOUTHERN CALIFORNIA WITH SURFACE HIGH PRESSURE BUILDING INTO THE GREAT BASIN. MODERATE TO STRONG NORTHWEST TO NORTH FLOW PATTERN WILL BRING HIGH END ADVISORY STRENGTH WINDS BELOW THE CAJON PASS AND IN THE SANTA ANA MOUNTAINS AND FOOTHILLS TODAY WITH GUSTS TO 50 MPH AND RELATIVE HUMIDITIES FALLING BELOW 10 PERCENT IN THE AFTERNOON. LATEST ACARS SOUNDINGS SHOW A STRONG SUBSIDENCE INVERSION AROUND 700 MB FAVORABLE FOR MOUNTAIN WAVE DEVELOPMENT. SOUNDINGS FROM LAX AND ONT SHOW STRONGEST WINDS IN THE MIXED LAYER BELOW 700 MB AND ABOVE THE NOCTURNAL SURFACE BASED RADIATIONAL INVERSION OF 25 TO 30 KNOT. THERE HAVE BEEN GUSTS TO 45 MPH AT FREMONT CANYON IN THE PAST TWO HOURS. STRONGER AND MORE WIDESPREAD SANTA ANA WINDS ARE EXPECTED FOR NORTHERN AREAS LATE TONIGHT THROUGH EARLY MONDAY AFTERNOON WITH ADVISORY STRENGTH SANTA ANA WINDS SPREADING INTO SOUTHERN AREAS BY MONDAY MORNING. WINDS MAY WEAKEN SOME MONDAY AFTERNOON AND EVENING WITH A SECOND ROUND OF STRONGER WINDS FOR LATE MONDAY NIGHT THROUGH TUESDAY MORNING. THIS IS NOT EXPECTED TO BE QUITE AS STRONG FOR NORTHERN AREAS...BUT MAY BE A LITTLE STRONGER FOR SOUTHERN AREAS AS THE OFFSHORE FLOW HAS A GREATER EASTERLY COMPONENT AT THAT TIME. 850 MB TEMPERATURES WILL SLOWLY WARM FOR TODAY AND MONDAY WITH GREATER WARMING FOR TUESDAY. HIGH TEMPERATURES FOR INLAND AREAS WILL WARM ONLY SLOWLY FOR TODAY AND MONDAY WITH GREATER WARMING TUESDAY. GREATER WARMING FASTER FOR AREAS CLOSER TO THE COAST. FOR LOW TEMPERATURES...HIGHER ELEVATIONS AND WIND SHELTERED AREAS WILL BE QUITE COOL WITH STEADILY WARMER FOR FOOTHILL LOCATIONS AND AREAS WITH OVERNIGHT MIXING FROM WIND. && .LONG TERM (WEDNESDAY THROUGH SATURDAY)... FAIR...WARM...AND DRY WITH WEAKER WINDS FOR WEDNESDAY AND THURSDAY. WEAK ONSHORE FLOW MAY RETURN BY LATE IN THE WEAK AS A WEAK TROUGH OF LOW PRESSURE DEVELOPS OFF THE CALIFORNIA COAST. THIS WILL BRING COOLING AND A RETURN OF THE MARINE LAYER. && .AVIATION... 121100Z...MODERATE OFFSHORE FLOW...CLEAR SKIES AND UNRESTRICTED VISIBILITIES ARE EXPECTED TODAY. STRONG OFFSHORE FLOW WILL DEVELOP TONIGHT...CAUSING GUSTY NORTH WINDS TO 65 MPH OVER THE RIDGES AND BELOW THE PASSES WITH ASSOCIATED WAVE...ROTOR...TURBULENCE AND AREAS OF BLOWING DUST. NORTH WINDS 30 TO 40 KTS AT 10000 FT AND 12 MB OFFSHORE SURFACE GRADIENTS SUPPORT A STRONG SANTA ANA WIND EVENT SUNDAY NIGHT THROUGH INTO TUESDAY. && .FIRE WEATHER... UPPER LEVEL LOW PRESSURE OVER THE CENTRAL AND SOUTHERN ROCKIES AND SURFACE HIGH PRESSURE OVER THE GREAT BASIN WILL COMBINE TO BRING PERIODS OF MODERATE TO LOCALLY STRONG SANTA ANA WINDS AT TIMES THROUGH TUESDAY WITH THE MOST WIDESPREAD CRITICAL FIRE WEATHER CONDITIONS MONDAY MORNING THROUGH TUESDAY AFTERNOON. A RED FLAG WARNING IS EFFECTIVE FOR NORTHERN AREAS LATER THIS MORNING AND BEGINNING MONDAY MORNING FOR SOUTHERN AREAS CONTINUING FOR BOTH AREAS THROUGH TUESDAY AFTERNOON. LONG DURATION LOW RELATIVE HUMIDITIES ARE POSSIBLE WEDNESDAY BUT WITH WEAKER WINDS. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...RED FLAG WARNING FROM 10 AM THIS MORNING TO 6 PM PDT TUESDAY FOR ORANGE COUNTY COASTAL AREAS-SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SANTA ANA MOUNTAINS- INCLUDING THE TRABUCO RANGER DISTRICT OF THE CLEVELAND NATIONAL FOREST. WIND ADVISORY FROM 10 PM THIS EVENING TO 12 PM PDT TUESDAY FOR ORANGE COUNTY COASTAL AREAS. HIGH WIND WARNING FROM 10 PM THIS EVENING TO 12 PM PDT TUESDAY FOR SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SANTA ANA MOUNTAINS AND FOOTHILLS. WIND ADVISORY FROM 6 AM THIS MORNING TO 10 PM PDT THIS EVENING FOR SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-SANTA ANA MOUNTAINS AND FOOTHILLS. RED FLAG WARNING FROM 6 AM MONDAY TO 6 PM PDT TUESDAY FOR RIVERSIDE COUNTY MOUNTAINS-INCLUDING THE SAN JACINTO RANGER DISTRICT OF THE SAN BERNARDINO NATIONAL FOREST-SAN BERNARDINO COUNTY MOUNTAINS-INCLUDING THE MOUNTAIN TOP AND FRONT COUNTRY RANGER DISTRICTS OF THE SAN BERNARDINO NATIONAL FOREST-SAN DIEGO COUNTY INLAND VALLEYS-SAN DIEGO COUNTY MOUNTAINS-INCLUDING THE PALOMAR AND DESCANSO RANGER DISTRICTS OF THE CLEVELAND NATIONAL FOREST. WIND ADVISORY FROM 6 AM MONDAY TO 6 PM PDT TUESDAY FOR RIVERSIDE COUNTY MOUNTAINS-SAN DIEGO COUNTY MOUNTAINS-SAN DIEGO COUNTY VALLEYS. PZ...NONE. && $$ PUBLIC...MARTIN AVIATION/MARINE...MACKECHNIE NWS ON THE WEB AT WEATHER.GOV/SANDIEGO